Typically, a subterranean well is provided with several sizes of more or less concentric pipe strings extending individually and successively, and with a diminishing tubular cross section, down to increasingly larger depths in the well. Pipes in such pipe strings typically are referred to as casings, liners, production tubings, injection tubings or similar. The primary object of the pipe string is to secure the well against external forces capable of causing well failure, and to prevent undesirable and unintentional flows of fluids within the well and/or out of the well. Typically, the deepest pipe string will penetrate one or more subterranean reservoirs containing, for example, oil, gas and/or water, whereas the opposite end of the pipe string typically will extend to the surface for recovery of such reservoir fluids or, alternatively, for injection of e.g. water and/or other injection fluids.
Between such successive pipe string sizes, and possibly between a pipe string and a surrounding borehole wall, one or more annuli will exist. In such annuli, various lines may be disposed so as to extend along a pipe string, the lines of which are normally attached on the outside of the pipe string. Such lines may comprise thin pipes or hoses, for example hydraulic pipes or chemical pipes, but also electric cables, fiber-optic cables or similar, possibly also associated support cables consisting of, for example, suitable wires or threads in order to unburden various loads, including tensile forces, acting on the lines along the pipe string. Such lines and possible support cables may be distributed individually around the circumference of the pipe string, and/or they may be arranged in one or more cable assemblies. In such a cable assembly, the lines commonly are cast into a sheath made of a flexible and protective material of a suitable type and shape, for example a rubber material or a plastics material. Typically, such lines are used to transmit various signals, including control signals and various data, and also motive power and/or various fluids between the surface and equipment disposed down within a well, and typically far down in the well. For this reason, such equipment typically is connected to a production tubing string or an injection tubing string, and commonly in context of so-called smart wells. Such downhole equipment, however, may also be placed at a shallower level in a well. This equipment may comprise various measuring instruments and monitoring equipment, for example equipment for measuring and monitoring pressure and temperature in a well. Such equipment may also comprise various ports, valves, actuators, hydraulic pistons, motors, pumps, supply equipment for various chemicals, injection equipment, gas lift equipment, etc., and also potential equipment for monitoring, controlling and/or driving the aforementioned equipment. Such equipment constitutes prior art.
Upon temporary or permanent abandonment of a well, it is customary to pressure-isolate one or more annuli and pipe bores along certain longitudinal intervals in the well, and particularly in or along one or more reservoir sections of the well. Normally, such pressure-isolation is carried out by conducting cement slurry into the/those annulus/annuli and pipe bore(s) of interest in the well, after which the cement slurry is allowed to harden therein.
Upon such cementation, however, continuous lines disposed in an annulus along a pipe string may constitute leakage channels for pressurized fluids residing in the well. If such leakage channels are not sealed so as to become pressure-isolated, the pressurized fluids unintentionally may flow onto other regions of the well, and possibly out of the well, which is not desirable. For this reason, it is customary for the operator of the well, and/or for the authorities of the particular country, to require that the lines are severed and possibly removed before initiating said cementation, and in such a manner that said cement slurry may surround the severed lines and possibly penetrate into the leakage channels that may be located therein. This is considered to be an adequate measure for ensuring that also the lines are pressure-isolated in context of cementation and plugging. In Norway, such statutory requirements are detailed in the official document termed NORSOK D-010, and the requirements are known well within the petroleum industry of Norway. Similar requirements also exist in other countries.
Nevertheless, there is a need in the industry for a more cost-efficient way of severing such longitudinal lines in a well, and without significantly weakening, in terms of strength, the integrity of the well. This is the need addressed, first and foremost, by the present method.